During exercise, the joints of an athlete's foot are subjected to most severe shear forces. In particular, the joint between the talus bone and the calcaneus bone, which forms the subtalar joint, is the recipient of a large portion of these shear forces. Primarily, these forces are the result of shocks generated when the heel strikes the ground. These shocks are exacerbated during running, since, during the running gait, both feet simultaneously leave the ground. As the heel strikes the ground during running, an increased motion occurs in all of the foot joints, with the forces distributed thereover by hydraulic action. This hydraulic action is due to the talar bones being held together by an integral network of muscles, tendons and ligaments that allow only limited motion, thus resulting in dispersion of the forces throughout the foot.
Although there is only limited motion between the talar bones, a certain amount of movement is provided in order to stabilize the foot on uneven surfaces. Such movements are inversion (pronation) which is turning of the foot inward and eversion (supination) which is turning the foot outward. When the heel of the foot strikes the ground, the remainder of the foot lags such that all of the weight is supported by the calcaneus bone. Until the distal portion of the foot strikes the ground, the foot is allowed to rotate about the subtalar joint which can cause excessive pronation. Normally, an adequate pair of athletic shoes can reduce this excessive pronation by providing arch support. However, athletic shoes have a tendency to slip during exercise and do not properly stabilize the subtalar joint. Moreover, an athlete's foot often swells during exercise, thus changing the fit and support of the athletic shoe during the exercise. If the subtalar joint and the joints therearound are not continually properly stabilized, pain can result from excessive rotation about these joints.
In view of the above, there exists a need for a stabilizing device that minimizes movement of the subtalar joint of the foot during exercise, and which may be adjusted during exercise in order to maintain proper support at all times.